Shares of Voyager Therapeutics (VYGR) are down 19% in after-hours trading to $18.50 after the company announced that Sanofi Genzyme (SNY) decided not to exercise its rights to the VY-AADC program for advanced Parkinson's disease.

As a result, Voyager gained full worldwide development and commercial rights to VY-AADC for the treatment of advanced Parkinson's disease. "We are very pleased to gain full worldwide rights to our Parkinson's disease program that recently demonstrated robust and durable clinical effects from the ongoing Phase 1b trial," said Steven Paul, Voyager's CEO.

He added, ""Sanofi Genzyme remains an important collaborator for Voyager, and we remain fully committed to progressing our Huntington's disease and Friedreich's ataxia programs under the ongoing collaboration."